JP5237438B2 - A subscriber node of a communication system with a functionally distinct transmission event memory - Google Patents

Description

  The present invention relates to a subscriber node of a communication system. The communication system includes a data bus connected to a subscriber node and at least one further subscriber node. The subscriber node has a communication controller for sending messages and / or receiving messages from the data bus and a message memory for temporarily storing messages to be sent or received. The invention further relates to a data bus and a plurality of subscriber nodes connected to the data bus for data transmission. Each subscriber node has a communication controller for sending messages and / or receiving messages from the data bus and a message memory for temporarily storing messages to be sent or received. . Finally, the invention relates to a method for transmitting a message from a first subscriber node of a communication system to a second subscriber node of the communication system via a data bus of the communication system. In this method, the application program of the first subscriber node stores the message to be transmitted in the message memory, and the message to be transmitted is read from the message memory by the communication controller according to the transmission command of the application program. And transmitted via the data bus.

  An example of a known communication system in the above form is a CAN (Controller Area Network) communication system. Here, in order to reduce the length of the wiring harness in the vehicle and thereby reduce the location and weight, it was developed in 1983 by Bosch for the construction of a network of control devices in the vehicle, In 1986 (see SAE Paper 860391, International Congress and Exposure, Detroit, Michigan, Feb. 24-28, 1986), an asynchronous serial bus system was introduced that was jointly introduced with Intel. However, the use of the CAN bus is not limited to the automobile field. In the meantime, the CAN bus has advanced into, for example, the building control technology and machine tool fields. In CAN, data transmission is performed in a data frame having not only user data (original message) to be transmitted but also setting data (header part) at the beginning and a check bit (CRC part) at the end of the frame. Another example of the known communication system of the above form is a FlexRay bus, a MOST (Media Oriented Systems Transport) bus, or an arbitrary field bus, for example, a LIN (Local Interconnect Network) bus.

  In the CAN and other protocols, the application program of the first subscriber node copies the message to be transmitted to the message memory, and the message to be transmitted is transmitted from the message memory in accordance with the transmission command of the application program. And the message is transmitted between the first subscriber node and the second subscriber node by being read by the rollers and transmitted via the data bus. At that time, there is often a need to notify the application program about the result of the transmission task and possibly cancellation of the transmission task. This is the case, for example, when another more urgent transmission task is entered during the execution of the transmission task. In such a case, the associated transmission task is canceled, but in some cases the transmission process that has already been started (the Start of Frame (SOF) bit has already been transmitted) is not interrupted. Continue until the arbitration is lost, an error occurs, or the message is sent successfully. Since data is transmitted serially in CAN and other protocols, it may take a relatively long time to reach the end of the data frame in some cases. During this time, the central processing unit (CPU) of the subscriber node needs to wait for the end of the data frame to arrive, so it is actually blocked. This can further lead to unacceptable delays when performing further transmission tasks that are more urgent.

  Only after the end of the data frame of the first transmission task is reached, the CPU can start the emergency transmission task. Further, the application program of the subscriber node copies the message transmitted from the emergency transmission task to the message memory, and the message transmitted from the message memory is transmitted by the communication controller according to the transmission command of the application program. It is read out and transmitted via the data bus. After processing the urgent transmission task, the application program continues the interrupted transmission again. For this purpose, the application program needs to be provided with information about the status of the send task processed before the emergency task. The application program should have the opportunity to be informed about the result of the transmission task and possibly the cancellation of the transmission task.

  Thus, in the case of a known subscriber node, the message memory to which the contents are transmitted is linked to the status bit. Often, the status bits only indicate the success of the send task. Some events may not be indicated by the status bits, especially in case of transmission task cancellation (Tx-Cancellation).

  Based on the above background art, the basis of the present invention is the problem of forming and developing subscriber nodes so that information about transmission tasks is managed and the information is accessible to application programs.

  In order to solve this problem, the subscriber node has at least one transmission event memory functionally distinguished from the message memory based on the subscriber node of the form mentioned at the beginning, and the transmission event memory includes Is proposed to store at least one transmitted or transmitted message.

  According to the present invention, the information about the transmission task is not stored in the message memory to which the content is transmitted, but is stored in a special list as a component of the transmission event memory. This means that the application program does not need to collect information from various message memories, the information can be called in a fixed location, preferably organized in time, and the message memory can be used to cancel the sending task. Later, it has the advantage that it can be used immediately without waiting for the result of the cancellation and will continue to be used. In particular, the CPU of the subscriber node starts to execute the next transmission task immediately after canceling the transmission task, for example, stores the message in a message memory. Of course, the CPU is also available for any other action after cancellation. With the present invention, execution of successive transmission tasks can also be accelerated upon cancellation of transmission tasks, improving CPU efficiency. Furthermore, the present invention has the advantage that the status flag for the status of the sending task is not linked to the message memory.

According to a preferred development of the invention, the transmission event is
-The message was sent successfully,
-The message was sent successfully despite the cancellation of the send task,
-Cancel send task, send process has not started yet,
-Canceling the send task, the send process is finished after arbitration is lost, and
-Cancel send task, send process finished after error,
It is proposed to include at least one of the following events.

  With the transmission event stored in the transmission event memory, the subscriber node's application program can also call the exact state or output of the preceding transmission task at any time. In addition to information on whether the data transmission was successful, in addition, information about in which situation the transmission was successful (without the sending task being canceled or despite the sending task being canceled) Whether the sending task was canceled and under what circumstances the sending task was canceled (for example, because the data bus was in use), the sending process has not yet started, the arbitration process is lost after arbitration is lost Information about which has ended or the transmission process has ended after an error) may also be called. This additional information allows the application program to take appropriate measures when continuing the data transmission in which the sending task was canceled, for example to give a new sending task.

  According to a preferred embodiment of the invention, it is proposed that the transmission event memory stores an identifier of at least one transmitted or transmitted message. The identifier preferably allows a unique identification of the message or sending task. A particular event when multiple transmission events for various transmission tasks are stored in the event memory by an identifier stored in the transmission event memory in addition to the transmission event for at least one transmitted or transmitted message A unique association of transmission events to a message or a specific transmission task is possible. Thus, a transmission event for a specific message or a specific transmission task can be read at any time within the range of the memory capacity of the event memory. The larger the event memory capacity, the more transmission events can be stored with associated information.

Of course, in addition to transmission events and identifiers, additional information can also be stored in the transmission event memory. So, for example,
The data length code of at least one transmitted or transmitted message,
-A time indicator indicating that an event has occurred,
The address of the message memory where the send task was issued, and
A sequence counter for identifying data packets when a relatively large amount of data is transmitted sequentially in multiple messages with the same identifier;
It is proposed that one or more of the information is stored in the transmission event memory.

  With additional information, management of stored transmission events by the application program can be reduced. The time indicator can be important for a particular application program. If a subscriber node has multiple transmission message memories (so-called transmission buffers), the address of the message memory from which the transmission task is issued can determine which transmission buffer is free for the new transmission task. it can. For example, when a subscriber node of a communication system configured as a controller is first newly programmed or programmed with a new software version at the end of a line or while in the factory, the sequence counter is For example, it may be important when downloading software. At that time, the software is divided into a plurality of, for example, 8-byte data packets, and the data packets have the same identifier. The sequence counter indicates for which data packet the transmission event was stored in the event memory or which data packet was successfully transmitted.

  Advantageously, the transmission event memory is organized as a FIFO (First In First Out) memory. Preferably, the transmission event memory includes a plurality of memory elements, and each memory element stores information on a transmitted or transmitted message. In practice, the capacity of event memory is generally filled by several memory elements. If there is a possibility that the capacity of the transmission event memory is exceeded because the application program hardly reads, a warning signal can be output. If the memory capacity is actually exceeded, an error signal can be output. Alternatively or additionally, it may be envisaged that the first stored entry is discarded if the capacity of the transmission event memory is exceeded.

  Advantageously, the transmit event memory includes a random access memory (RAM). Furthermore, other implementations, such as implementations using flip-flops, can be envisaged, but this implementation requires a relatively large silicon area and therefore causes a relatively high cost. The arrangement of the invention in which the transmission event memory is configured as part of the message memory is particularly advantageous. Despite the functional distinction between message memory and transmission event memory, both in terms of hardware can be configured in the same memory element but in different memory areas. Advantageously, the size of the transmission event memory, in particular the number of memory elements of the event memory, can be freely set with respect to the software, for example by means of setting bits. In this way, the size of the event memory can be flexibly adjusted for individual requests in a simple manner.

  As a further solution to the problem of the invention, based on a communication system of the form listed at the beginning, at least one subscriber node has at least one transmission event memory functionally distinguished from the message memory, The event memory stores transmission events for at least one transmitted or transmitted message. According to a preferred development, the at least one subscriber node of the communication system according to the invention further comprises the features as claimed in one or more of claims 2-8.

  Finally, as yet another solution of the present invention, a transmission event for a transmitted or transmitted message is functionally distinguished from the message memory, based on the message transmission method according to the form mentioned at the beginning. It is proposed that the application program stored in the transmission event memory can access the information stored in the event memory at any time.

In the following, preferred embodiments of the present invention will be described in detail with reference to the drawings.
It is an example of the communication network concerning this invention. 2 is an example of a subscriber node according to the present invention of the communication network of FIG. 2 is a flowchart of a method according to the present invention for message transmission via the communication network of FIG.

  In FIG. 1, the entire communication system according to the present invention is denoted by reference numeral 1. The network 1 includes a data bus 2 symbolically indicated by a single line. Of course, the data bus 2 can be configured as one, two or a plurality of wired buses. The physical layer of the data bus 2 may include one or more copper wires, one or more glass fiber wires, or optical communication (eg, infrared) or wireless communication. A plurality of subscriber nodes 3 are connected to the data bus 2, and three of them are illustrated in FIG. Each node 3 is connected to the data bus 2 via a communication module 4 (so-called communication controller, communication controller: CC). Further, the node 3 has a host application 5 (so-called application program: Application program: AP).

  The message 7 can be transmitted via the data bus 2 according to a serial communication protocol (for example, CAN, FlexRay, LIN, MOST, etc.). The communication module 4 plays a role of transmitting and receiving the message 7 via the data bus 2. Each message 7 has a header 8 with an identifier (so-called Identifier) and a further set bit. In addition to the header 8, the message 7 has a user data portion 9 (so-called payload) and a so-called trailer 10. The identifier enables a unique identification of the message 7. In CAN (Controller Area Network), the identifier is, for example, a kind of transmission address that enables confirmation of the sender of the message 7 and reveals the content 9 of the message 7.

  Logically, a transmission buffer 11 (Tx) and a reception buffer 12 (Rx) are arranged between the application program 5 and the communication controller 4 as temporary memories for outgoing or arriving messages 7. Physically, the message memories 11 and 12 are components configured integrally with the communication controller 4, or can be configured separately from the communication controller 4. The message memories 11, 12 are preferably configured in the form of a FIFO. The message memories 11 and 12 are configured as, for example, arbitrarily accessed memories (so-called RAMs).

  When one application program 5 of the subscribers 3 wants to transmit the message 7 to the other subscribers 3 via the data bus 2, first the transmitted message 7 or its contents 9 is transmitted to the transmission buffer 11. (Arrow 20 in FIG. 2). In response to the transmission command of the application program 5, the communication controller 4 reads the message 7 or its contents 9 from the transmission buffer 11 (arrow 21 in FIG. 2), and according to the communication protocol in which the message 7 is transmitted in the communication system 1. Thus, the message 7 or its content 9 is in the correct format (for example, the addition of the header 8 and trailer 10), and the message 7 is transmitted via the data bus 2 (arrow 22 in FIG. 2). Since the message 7 is serially transmitted via the data bus 2, it may take a relatively long time. The invention relates to the case where at any point during the execution of the transmission task, the transmission task is canceled again, for example because another transmission task in particular should be executed first (so-called, Cancel transmission). The transmission task starts with the storage of the message 7 or its contents 9 in the transmission buffer 11 and ends with the reception of feedback from the communication controller 4 as to whether or not the message has been transmitted successfully.

  In such a case as well as in other cases, the application program 5 needs to be notified of the result of the transmission task and possibly cancellation of the transmission task. Therefore, in the prior art, the transmission buffer 11 is connected to a status bit that can convey information as to whether or not the transmission task has been successfully processed. Information about further events is not available from the status bits, especially when canceling the send task. In CAN, when a transmission task is canceled, a transmission process that has already started (that is, a start-of-frame (SOF) has already been transmitted) is not interrupted. Continue until the arbitration is lost, an error occurs, or the message is sent successfully. The application program 5 cannot obtain information from the status bits about which event last occurred after canceling the transmission task. Further, the application program 5 needs to wait for a transmission task event, and is blocked to some extent during this time. In this respect, the present application may provide an improvement plan.

  According to the present invention, each subscriber node 3 is provided with a transmission event memory 13 (Tx Stat) that is functionally distinguished from the message memories 11 and 12, respectively. A transmission event or state for at least one transmitted or transmitted message 7 is stored. As a matter of course, it is not necessary for all the subscriber nodes 3 of the communication network 1 to be provided with the transmission event memory 13. The event memory 13 is preferably configured as a memory (RAM) that is optionally accessed and organized in the form of a FIFO. Of course, the event memory 13 can also be configured as a read-only memory (eg, flash memory, ROM, EEPROM). The event memory 13 can be configured as a component configured integrally with the communication controller 4 or separately from the communication controller 4. Further, the transmission event memory 13 can be configured separately from the message memories 11 and 12 or as a part of the message memories 11 and 12. When the event memory 13 is a part of the message memories 11 and 12, the size of the event memory 13 can be flexibly determined according to individual requests, for example, by setting bits with respect to software.

  Information about the state of the sending task is also no longer stored in the message memory 11 to which its contents are sent, but in a special sending event list. This transmission event list advantageously includes an entry for each transmission event or cancellation event. According to the present invention, information about the state of the transmission task can be managed in the communication module 4 and stored in the event memory 13 (arrow 23 in FIG. 2). The application program 5 can flexibly read out the information stored in the event memory 13 (arrow 24 in FIG. 2). It is particularly advantageous that the information about the transmission task is now completely separated from the transmission buffer 11. A further advantage is that the application program 5 no longer needs to collect state information about the sending task from the various message memories 11 and is suitable where the information is fixed (in the sending event list in the sending event memory 13). It can be called after being arranged in time. After canceling the send task, the message memory 11 is immediately available again without having to wait for the send task or the result of the cancel. The application program 5 can read the information stored in the event memory 13 at a later time, and does not need to respond immediately (for example, for each interrupt). If there is a risk that the application program 5 will rarely read and exceed the capacity of the event memory 13, a warning signal is output in the first step, and the warning signal is an accelerated read of at least a portion of the information. Or a corresponding countermeasure for more frequent readouts. When the capacity of the memory 13 is actually exceeded, an error signal can be output. In this case, the oldest entry in the transmission event memory 13 can be discarded each time to make room for information on the current transmission task.

In the simplest case, the event memory 13 contains the time-sequential events of the transmission task (message 7 was transmitted and the transmission task was canceled). In the following, some further examples of events that can be stored in the event memory 13 will be described.
1) Message 7 was sent successfully,
2) Despite canceling the send task, message 7 was sent successfully,
3) The send task is canceled and the send process is not started,
4) The send task is canceled and the send process is terminated after arbitration is lost, and
5) The send task was canceled and the send process was terminated after an error.

In addition to the transmission event for the message 7 to be transmitted or transmitted, the transmission event memory 13 can also store further additional information. The information content of the memory element of the memory 13 has various expansion stages. Preferably, the memory 13 also stores an identifier of the message 7 (for example, a CAN identifier). Since identifiers allow unique identification and association of stored information for a particular message, messages need not necessarily be stored in memory 13 in the order in which they occurred. The following additional information:
1) a data length code indicating the length of the user data part 9 of at least one transmitted or transmitted message 7;
2) A time indicator indicating when the event stored in the memory 13 has occurred;
3) The address of the message memory 11 where the transmission task is issued, and
4) A sequence counter for identifying a data packet when a relatively large amount of data is sequentially transmitted in a plurality of messages 7 having the same identifier by a higher-order transmission protocol,
It is also conceivable to record one or more of them in the transmission event memory 13.

  With additional information, management of stored transmission events by the application program 5 can be reduced. The time indicator may be important for a particular application program 5. When the subscriber node 3 has a plurality of transmission buffers 11, it is possible to confirm which transmission buffer 11 is free for a new transmission task by the address of the message memory 11 from which the transmission task is issued. For example, when the subscriber node 3 of the communication network 1 configured as a controller at the end of the line or while in the factory is first newly programmed or programmed with a new software version. The counter may be important when downloading software, for example. At that time, the software is divided into a plurality of, for example, 8-byte data packets, all of which have the same identifier. The sequence counter indicates for which data packet the transmission event was stored in the event memory 13 or which data bucket was successfully communicated. The sequence counter is registered in the message memory 11 by the application program 5 when a transmission task is assigned.

  In the following, the method according to the present invention will be explained in detail using the flowchart shown in FIG. The method begins at function block 30. In the function block 31, the application program 5 transmits the data to be transmitted to the transmission buffer 11. The application program 5 transmits a transmission command in the function block 32. In response to the transmission command, the communication controller 4 reads data from the transmission buffer 11 in the function block 33. Subsequently, the controller 4 puts the data 9 in a message corresponding to the communication protocol used in the function block 34 and puts the data in a corresponding format. Thereafter, in function block 35, message 7 is serially transmitted via data bus 2. Message transmission starts with the transmission of the SOF bit.

  At any point during the execution of the send task (function blocks 31-35), events that require cancellation of the send task, for example other messages that are more urgent and important than the message of the current send task, are possible There may be a desire to send as soon as possible. The occurrence of such an event is illustrated by function block 36 in FIG. In the example shown, event 36 occurs during serial message transmission. The application program 5 cancels the current transmission task.

  In a function block 37, the application program 5 can store new data, ie more urgent or more important message 7 data in the transmission buffer 11 again immediately after canceling the transmission task. The application program 5 does not have to wait for the end of transmission of the first message 7 or the event of the first transmission task. As a result, the utilization and efficiency of the host CPU can be improved. The state of the first transmission task is stored in the transmission event memory 13 by the communication controller 4 at a later time after the end of transmission of the first message. This can be done at any time after the transmission of the first message and is illustrated in FIG.

  In a function block 39, the application program 5 sends a send command for further message transmission. In response to the transmission command, the communication controller 4 reads new data from the transmission buffer 11 in the function block 40. Subsequently, in the function block 41, the controller 4 puts the data 9 into the second message 7 corresponding to the communication protocol to be used, and converts the data into a corresponding format. Thereafter, in function block 42, the second message 7 is transmitted serially via the data bus 2. Message transmission starts with the transmission of the SOF bit. The state of the second transmission task is stored in the transmission event memory 13 by the communication controller 4 at any later time after the transmission of the second message. This is illustrated by functional block 43 in FIG.

  At any time after the end of transmission of the first message 7, the application program reads the event of the first transmission task from the transmission event memory 13. This is done in the example shown after the end of the transmission of the second message in function block 44 that caused the cancellation of the first sending task. According to the read event of the first sending task, the application program 5 prompts a new transmission of the first message 7 at function block 45 (the message has not been sent successfully), or Do not prompt for a new transmission of the first message 7 (the message has been sent successfully). The method then ends at function block 46.

An important aspect of the present invention is that the utilization of the host CPU is improved, the transmission of a new message can be started within the shortest time after the transmission task is canceled, and more detailed information about the individual transmission task is provided. In other words, the storage of information about the transmission task in the event memory and the reading of the information are separated in time, which prevents the host CPU from being blocked.

Claims (8)

A subscriber node (3) of a communication system (1) comprising a data bus (2), said data bus (2) comprising said subscriber node (3) and at least one further subscriber node ( 3) and the subscriber node (3) transmits the message (7) via the data bus (2) and / or receives the message (7) from the data bus (2) In the subscriber node (3), comprising a communication controller (4) for transmitting and a message memory (11, 12) for temporarily storing messages (7) to be transmitted or received,
The subscriber node (3) has at least one transmission event memory (13) functionally distinguished from the message memory (11, 12), and the transmission event memory (13) includes at least one transmission event memory (13). A transmission event for one transmitted or transmitted message (7) is stored ;
The transmission event memory (13) is configured as a part of the message memory (11, 12),
The subscriber node (3) is characterized in that the size of the transmission event memory (13) can be set by a setting bit . The transmission event is:
-Message (7) was sent successfully,
-Message (7) was sent successfully despite the cancellation of the send task,
-Cancel send task, send process has not started yet,
-Canceling the send task, the send process is finished after arbitration is lost, and
-Cancel send task, send process finished after error,
The subscriber node (3) according to claim 1, characterized in that it comprises at least one of the following events:   3. Subscriber node (3) according to claim 1 or 2, characterized in that the transmission event memory (13) stores an identifier of at least one transmitted or transmitted message (7). ). The data length code of the at least one transmitted or transmitted message (7),
A time indicator indicating that the transmission event has occurred;
- Send address of the message memory the task is issued (11, 12) and,
- when a relatively large amount of data, successively sent in multiple messages with the same identifier (7), sequence counter identifying the data packet,
The subscriber node (3) according to any one of claims 1 to 3, characterized in that one or more of the following information is stored in the transmission event memory (13).   The transmission event memory (13) comprises a plurality of memory elements, each memory element storing information for a message (7) to be transmitted or transmitted. Subscriber node (3) according to any one of the preceding claims.   The subscriber node (3) according to any one of the preceding claims, characterized in that the transmission event memory (13) comprises a memory that is optionally accessed. A communication system (1) comprising a data bus (2) and a plurality of subscriber nodes (3) connected to the data bus (2) for data transmission, wherein each of the subscriber nodes (3) A message (7) to be transmitted or received via the data bus (2) and / or a communication controller (4) for receiving a message (7) from the data bus (2); 7) a message memory (11, 12) for temporarily storing the communication system (1),
The at least one subscriber node (3) has at least one transmission event memory (13) functionally distinguished from the message memory (11, 12), the transmission event memory (13) A transmission event for at least one transmitted or transmitted message (7) is stored ;
The transmission event memory (13) is configured as a part of the message memory (11, 12),
The communication system (1), wherein the size of the transmission event memory (13) can be set by a setting bit . A message is sent from the first subscriber node (3) of the communication system (1) to the second subscriber node (3) of the communication system (1) via the data bus (2) of the communication system (1). (7), the application program (5) of the first subscriber node (3) copies the message (7) to be transmitted to a message memory (11, 12), and the message The message (7) to be transmitted is read from the memory (11, 12) by the communication controller (4) in response to the transmission command of the application program (5), and via the data bus (2). Transmitted in said method,
A transmission event for a transmitted or transmitted message (7) is stored in at least one transmission event memory (13) that is functionally distinct from the message memory (11, 12), and the application program ( 5) Ri always accessible der the transmission events stored in the transmission event memory (13),
The transmission event memory (13) is configured as a part of the message memory (11, 12),
Method according to claim 1, characterized in that the size of the transmission event memory (13) can be set by setting bits .

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